Pangasinan was among the earliest political and administrative units in the Philippines. It was officially conquered and colonized by D. Martin de Goiti in 1571. On April 5, 1572, Pangasinan was made an encomienda by the Spanish royal crown to receive instruction on the Catholic Faith, which means that Pangasinan was organized under one leadership and has identity before the Spanish royal court. Eight years later, in 1580, Pangasinan was organized into a political unit under an alkalde mayor who at that time has authority as head of the province or provincial government with judicial function indicating that Pangasinan has become a province. To commemorate the day when Pangasinan became an encomienda and the year it became a province, Pangasinan celebrates April 5, 1580 as the official founding day of the Province of Pangasinan. At that time, its territorial jurisdiction included the Province of Zambales and parts of La Union and Tarlac. By the middle of the 19th century however, the northern towns of Agoo to Bacnotan were separated from the province and became parts of La Union. The provincial territory was further diminished in 1875 with the annexation of Paniqui and other towns south of it to Tarlac.

Pangasinan, derived its name from the word “panag asinan”, which means “where salt is made”, owing to the rich and fine salt beds which were the prior source of livelihood of the province’s coastal towns.